U.S. patent application number 12/565861 was filed with the patent office on 2010-01-21 for motor vehicle battery disconnect circuit having electronic disconnects.
This patent application is currently assigned to International Truck Intellectual Property Company, LLC. Invention is credited to Clayton M. Howell, John D. Jervis, H. Edward Kelwaski.
Application Number | 20100013302 12/565861 |
Document ID | / |
Family ID | 39260468 |
Filed Date | 2010-01-21 |
United States Patent
Application |
20100013302 |
Kind Code |
A1 |
Howell; Clayton M. ; et
al. |
January 21, 2010 |
Motor Vehicle Battery Disconnect Circuit Having Electronic
Disconnects
Abstract
An electronic disconnect switch module (12) in a motor vehicle
has one or more pairs of high-current, high-side solid state switch
devices (30A, 30B, 32A, and 32B). The source terminal of one device
of each pair is connected to vehicle load circuits (27), the source
terminal of the other device of each pair is connected to the
vehicle battery bank (16), and the drain terminals of the devices
of each pair are connected in common. The module also has a
microcontroller (34) that interfaces the switch devices with the
vehicle electrical system. Four feature groups are provided:
Vehicle Electrical System Protection, Battery Charge Control,
Battery Disconnect, and Battery Monitoring.
Inventors: |
Howell; Clayton M.; (Fort
Wayne, IN) ; Jervis; John D.; (Fort Wayne, IN)
; Kelwaski; H. Edward; (Craigville, IN) |
Correspondence
Address: |
International Truck Intellectual Property Company,
4201 WINFIELD ROAD
WARRENVILLE
IL
60555
US
|
Assignee: |
International Truck Intellectual
Property Company, LLC
Warrenville
IL
|
Family ID: |
39260468 |
Appl. No.: |
12/565861 |
Filed: |
September 24, 2009 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
11536959 |
Sep 29, 2006 |
7612524 |
|
|
12565861 |
|
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Current U.S.
Class: |
307/10.7 |
Current CPC
Class: |
H02J 7/1438 20130101;
H02J 7/00304 20200101; H02J 7/00306 20200101; Y02T 10/70 20130101;
H02J 7/0029 20130101; Y02T 10/7005 20130101; H02J 7/1461
20130101 |
Class at
Publication: |
307/10.7 |
International
Class: |
H02H 7/18 20060101
H02H007/18 |
Claims
1-10. (canceled)
11. A disconnect switch module for disconnecting a battery bank
from an electrical load upon occurrence of certain conditions, the
module comprising one or more pairs of high-current, high-side
solid state switch devices, the devices of each pair each
comprising a solid-state switch comprising a source terminal and a
drain terminal providing a conduction path through the switch, the
source terminal of one device of each pair being connected to the
load circuits, the source terminal of the other device of each pair
being connected to the battery bank, and the drain terminals of the
devices of each pair being connected in common.
12. A module as set forth in claim 11 further comprising a
processor that is associated with each solid-state switch and that
comprises an algorithm for processing data relevant to operation of
the disconnect switch module and for developing from that processed
data control data for controlling the solid-state switches.
13. A module as set forth in claim 12 wherein the data relevant to
operation of the module includes data representing a) the magnitude
and direction of electric current flow through the module with
respect to the battery bank, and b) the open circuit voltage of the
battery bank.
14. A module as set forth in claim 13 wherein the control data for
controlling the disconnect switch module is developed by also
processing programmed data defining the number of batteries in the
battery bank and the ampere-hour rating of each battery in the
battery bank.
15. A module as set forth in claim 12 wherein the processor
comprises an algorithm that when executed, develops data that
causes either a) limiting battery bank charge current to a defined
charge current limit without regulating battery bank voltage, b)
regulating battery bank voltage to a first defined limit of
regulation when charge current is within a defined range
immediately below the defined charge current limit, or c)
regulating battery bank voltage to a second defined limit of
regulation that is less than the first defined limit of regulation
when charge current is less than the defined range.
16. A module as set forth in claim 12 wherein the module comprises
a reset input for resetting the module from a disconnected state to
a connected state in response to a reset input signal.
17. A module as set forth in claim 12 wherein the module comprises
an input for switching the module from a connected state to a
disconnected state in response to a disconnect input signal.
18. A module as set forth in claim 11 further comprising a
processor that is associated with each solid-state switch and that
comprises an algorithm for processing data corresponding to battery
bank voltage for causing the solid-state switches to disconnect the
battery bank from the electrical load when data corresponding to
battery bank voltage indicates battery bank voltage has dropped
below a low voltage threshold.
19. A module as set forth in claim 11 further comprising a
processor that is associated with each solid-state switch and that
comprises an algorithm for processing data corresponding to battery
bank voltage for causing the solid-state switches to disconnect the
battery bank from the electrical load when data corresponding to
battery bank voltage indicates a reversed polarity battery in the
battery bank.
20. A module as set forth in claim 11 further comprising a
processor that is associated with each solid-state switch and that
comprises an algorithm for processing data corresponding to battery
bank voltage for causing the solid-state switches to disconnect the
battery bank from the electrical load when data corresponding to
battery bank voltage indicates that a battery has been connected in
the battery bank to create a double battery.
21-26. (canceled)
Description
FIELD OF THE INVENTION
[0001] This invention relates generally to electrical systems of
motor vehicles. More particularly, the invention relates to battery
disconnect devices and circuits for preventing battery drain that
can occur, for example, when an engine-driven alternator does not
operate for an extended period of time due to the engine being shut
off and therefore is unable to maintain battery charge.
BACKGROUND OF THE INVENTION
[0002] Certain motor vehicles, heavy trucks that are powered by
diesel engines for example, may be parked for extended periods of
time. If the engine is allowed to keep running after a truck has
been parked, the alternator should be effective to keep the truck's
battery bank charged. If the engine is shut down, either
intentionally by the driver, or automatically by a device such as
an idle shutdown timer, while the circuits for electric devices
remain on, the battery bank will begin to drain through those
circuits. For example, an ignition switch will typically remain on
after an idle shutdown timer has timed out, and certain circuits
that are fed through the ignition switch and may have been left on
may continue to draw current.
[0003] Because the battery bank must be able to provide sufficient
current for cranking the engine at starting, the battery bank of a
diesel-powered heavy truck typically comprises multiple storage
batteries ganged together in parallel. If the battery bank is
allowed to drain to the point where it cannot deliver the large
cranking current necessary for starting the engine, the vehicle
cannot be operated. Because a heavy truck may be parked for an
extended period of time, it is therefore appropriate to guard
against the possibility that its battery bank will be drained to a
point that will not allow engine to be started or cranked due to
failure to turn off all its electric circuits.
[0004] Consequently, it is known to place a disconnect switch in
circuit between the battery bank and the rest of the vehicle
electrical system for use in disconnecting the battery bank from
the electrical system to prevent battery current draw that, if
allowed to continue long enough, could drain the battery bank to
the point of preventing the engine from being cranked and
started.
[0005] Commonly owned U.S. Pat. No. 6,836,094 discloses an example
of a battery disconnect circuit that has the advantage of a direct,
switch-free connection of the battery bank to the cranking motor so
that when the cranking motor solenoid is energized to crank the
motor, cranking current flows directly from the battery bank to the
cranking motor windings, and not through the disconnect switch.
[0006] Battery disconnect switches are typically electromechanical
devices, not solid-state devices. The solid-state counterparts of
certain electromechanical devices can often, but not always,
provide significant advantages in performance and/or function
and/or cost. Sometimes no comparable solid-state counterpart exists
for an electromechanical device. For various reasons
electromechanical devices continue to enjoy significant usage in
the automotive industry, and it is believed reasonable to include
battery disconnect switches in that category.
[0007] When an electromechanical battery disconnect switch fails,
it is typically replaced, but sometimes it is simply bypassed for
expediency. The inherent nature of such a switch seems to render it
poorly suited for interfacing with vehicle electrical systems that
have become largely electronic over the past several decades.
Consequently, electronic monitoring of such switches for
diagnostic, data collection, and other various purposes appears to
have been largely ignored.
SUMMARY OF THE INVENTION
[0008] The present invention is believed to represent an advance in
motor vehicle electrical system technology through employing known
solid-state devices in a unique way to create an electronic battery
disconnect switch module that provides the benefits of solid-state
construction and that enables versatile interfacing with a
vehicle's electrical system, a capability apparently previously
unavailable with electromechanical battery disconnect switches.
[0009] The solid-state devices that form the inventive disconnect
switch within the module are sometimes known as "high-current,
high-side" switches. An example of such a device is one sold by
Freescale Semiconductor, Inc. (Models 33982 and 33982B).
[0010] The exemplary module possesses its own processing features
and an interface that allows data communication with a vehicle's
own processing system. These attributes of the module endow an
electronic battery disconnect switch with certain multi-function
capabilities that are useful in battery voltage monitoring,
rate-of-charge control, and circuit protection, all while still
fulfilling the basic purpose of avoiding battery draining to the
point of preventing the engine from being cranked and started. The
exemplary embodiments to be described here show a novel
configuration of high-current, high-side switches associated with a
microprocessor in the module that provide functions by four feature
groups referred to for convenience as: Vehicle Electrical System
Protection; Battery Charge Control; Battery Disconnect; and Battery
Monitoring. The solid-state switches perform the Feature Group
functions through the microcontroller interface with the vehicle's
electrical system. The microcontroller contains all necessary
algorithms to perform the tasks contemplated by the Feature Group
functions, principally handling/controlling load current through
the solid-state switches and reporting diagnostic information.
[0011] Vehicle Electrical System Protection is intended to protect
the entire electrical system of the vehicle and all electrical
circuits/components on the vehicle from "reverse battery" and
"double battery" jump-start conditions.
[0012] Battery Charge Control controls the rate of charge from the
engine-driven alternator to the battery bank.
[0013] Battery Disconnect disconnects the battery bank from the
vehicle electrical system through either automatic or manual
operation as described hereinafter.
[0014] Battery Monitoring uses a method described in U.S. Pat. No.
6,417,668 to determine the battery condition in the battery
bank.
[0015] The use of high-current, high-side semiconductor switches as
the disconnect elements, with appropriate cooling techniques for
solid-state devices that carry large electrical currents, can
improve quality, reliability, and life expectancy of battery
disconnect switches while at the same time providing additional
diagnostic and protection features to vehicle electrical system.
Improved quality, reliability, and life expectancy are achieved
through a combination of the low "on resistance" of the
semiconductor switches and effective control of their operating
temperature.
[0016] Through the four feature groups described above, the
invention is capable of measuring and reporting net battery
current, battery charge current, and net battery voltage. An
additional advantage will be the ability to detect and protect the
vehicle batteries from excess drain. Once the battery drain
threshold has been reached, the switches will shut off current to
the current-draining electrical loads automatically to ensure
enough residual battery charge capacity for engine cranking and
starting. Still another advantage provided by the invention is
protecting vehicle electrical systems from abnormal voltage events,
such as a reverse battery connection and 24V jump-start applied to
a 12V system. The invention can also monitor and log occurrence of
such events for use in fleet management or maintenance.
[0017] The disclosed embodiment of inventive disconnect switch
module contains two inputs that allow the use of low current input
signals. One input signal is a manual disconnect input, thus
allowing this device to act as a Master Disconnect Switch as
required by certain industry standards. The other input signal is a
reset input that can reset the disconnect switch module from off
(disconnected) to on (connected). The reset signal is applied to
the disconnect switch module by a reset switch that is accessible
to the driver. The disconnect switch module also has a high-side
output, connected to an indicator, such as an LED that may even be
built into the reset switch, for signaling the driver that the
disconnect switch module is off and has disconnected the battery
bank from the vehicle electrical loads. The reset switch provides a
mechanism to power up the vehicle electrical system after the
disconnect switch module has disconnected the vehicle battery bank
because of an event described in the feature group.
[0018] All of the information that the inventive disconnect switch
module collects is made available on a standard vehicle datalink
(SAE Standard J1939). Other electronic devices on the vehicle
datalink, such as the Vehicle Body Controller, the Electronic Gauge
Cluster (EGC) and the Aware Module, can request this information as
needed from the inventive disconnect switch module.
[0019] Because the inventive disconnect switch module is on the
vehicle datalink, certain devices such as the International Aware
Module have the ability to command and control certain aspects of
disconnect switch functionality for purposes such as theft
avoidance/deterrence, fleet management and general TM maintenance.
The Aware Module is a data collection and communications system
that, when installed into a vehicle, can gather diagnostic,
prognostic and vehicle location information, primarily from the SAE
J1939 data link and various sensors connected to the module.
[0020] One example of an installation for a battery disconnect
switch involves the use of two heavy conductors, one to connect the
battery terminal of the disconnect switch to a terminal of the
battery bank, such as the positive terminal in a negative ground
electrical system, and another to connect the load terminal of the
disconnect switch to a distribution point for the electrical system
load, with the alternator output terminal being connected to the
load terminal of the disconnect switch.
[0021] Another example of an installation for a battery disconnect
switch is like the one described but with the alternator connected
to the battery terminal of the disconnect switch. In each of these
two examples, the path for cranking current flow from the battery
bank to the starting motor is switch-free.
[0022] The inventive disconnect switch module is disclosed here in
use in each of those two examples.
[0023] One general aspect of the invention relates to an
engine-powered land vehicle comprising an engine, a drivetrain
through which the engine propels the vehicle on land, a battery
bank comprising one or more D.C. storage batteries, an electric
starter motor that draws current from the battery bank to crank the
engine at starting, and electric load circuits that are fed from
the battery bank through a disconnect switch.
[0024] The disconnect switch comprises one or more pairs of
high-current, high-side solid state switch devices. The devices of
each pair each comprise a solid-state switch comprising a source
terminal and a drain terminal providing a conduction path through
the switch. The source terminal of one device of each pair is
connected to the load circuits, the source terminal of the other
device of each pair is connected to the battery bank, and the drain
terminals of the devices of each pair are connected in common. The
high-current, high-side solid state switch devices are associated
with a microcontroller in a disconnect switch module. It is through
the microcontroller that the module interfaces with the vehicle
electrical system.
[0025] Another aspect of the invention relates to a disconnect
switch module for disconnecting a battery bank from an electrical
load upon occurrence of certain conditions. The module comprises
one or more pairs of high-current, high-side solid state switch
devices, the devices of each pair each comprising a solid-state
switch comprising a source terminal and a drain terminal providing
a conduction path through the switch, the source terminal of one
device of each pair being connected to the load circuits, the
source terminal of the other device of each pair being connected to
the battery bank, and the drain terminals of the devices of each
pair being connected in common. This arrangement provides a
bi-directional conduction capability through each pair of
devices.
[0026] Still another aspect of the invention relates to a method
for protecting a battery bank having one or more D.C. storage
batteries in an electrical system of an engine-powered land vehicle
against loss of charge that renders the battery bank incapable of
operating an electric starter motor that draws current from the
battery bank to crank the engine at starting. The electrical system
has electric load circuits that are fed from the battery bank
through a disconnect switch module that comprises controlled
conduction solid-state switch devices through which current can
bi-directionally flow between the battery bank and the electric
load circuits.
[0027] The method comprises processing data relevant to operation
of the solid-state switch devices and developing from that
processed data control data for controlling the solid-state
switches to either a) limit charge current to the battery bank to a
defined charge current limit without regulating battery bank
voltage, b) regulate battery bank voltage to a first defined limit
of regulation when charge current is within a defined range
immediately below the defined charge current limit, or c) regulate
battery bank voltage to a second defined limit of regulation that
is less than the first defined limit of regulation when charge
current is less than the defined range.
[0028] The foregoing, along with further aspects, features, and
advantages of the invention, will be seen in the following
disclosure of a presently preferred embodiment of the invention
depicting the best mode contemplated at this time for carrying out
the invention. The disclosure includes drawings, briefly described
as follows.
BRIEF DESCRIPTION OF THE DRAWINGS
[0029] FIG. 1 is a schematic electric circuit diagram of a first
embodiment of the present invention in a motor vehicle electrical
system.
[0030] FIG. 2 is a schematic electric circuit diagram of a second
embodiment.
[0031] FIG. 3 is a more detailed electric circuit diagram of
battery disconnect switches present in the embodiments of FIGS. 1
and 2.
[0032] FIG. 4 is an electric circuit diagram that shows additional
portions of the vehicle electrical system in association with the
disconnect switches.
[0033] FIG. 5 is a detailed block diagram of elements internal to
an exemplary high-current, high-side switch used in the inventive
battery disconnect switch.
[0034] FIGS. 6A and 6B together comprise a flow diagram for an
algorithm that is used with the Battery Charge Control feature
group.
DESCRIPTION OF THE PREFERRED EMBODIMENT
[0035] FIG. 1 shows a portion of a motor vehicle electrical system
10 that incorporates an electronic disconnect switch module 12 in
accordance with principles of the present invention. While the
particular example of motor vehicle shown is a truck powered by a
diesel engine 14, principles of the invention can be applied to
various vehicles where use of a disconnect switch is desired.
[0036] Electrical system 10 comprises a battery bank 16 containing
one or more individual D.C. storage batteries 18. In a heavy truck
powered by a diesel engine, battery bank 16 contains multiple
batteries 18 ganged together as shown. When engine 14 is running,
batteries 18 are kept charged by an engine-driven alternator 20
having positive and negative terminals 20A, 20B. Terminal 20A is
connected to a terminal 12B on the load side of switch module 12,
and the positive battery terminals are connected to a terminal 12A
on the battery side of the switch module.
[0037] Running of the engine is under the control of a switch that
is typically key-operated, keyswitch 22, and that is commonly
referred to as an ignition switch, even in a vehicle whose engine
relies on compression of fuel in the engine cylinders for ignition
rather than on spark ignition.
[0038] FIG. 1 depicts a positive voltage electrical system where
the negative battery terminals are grounded, as is alternator
terminal 20B, and where the positive battery terminals are
connected to one terminal 24A of a starter motor solenoid 24 for
operating an electric starter motor 26 for cranking engine 14 at
starting.
[0039] Solenoid 24 may be integrated with starter motor 26 so that
other than terminal 24A, the only external terminals of the
combined devices to which conductors attach are a common ground
terminal 26B and a terminal for energizing a coil 24S of solenoid
24 that is in circuit between keyswitch 22 and ground terminal 26B.
Solenoid 24 further comprises an armature that is operated by coil
24S and that carries a contact 24C.
[0040] When coil 24S is not energized, as shown in FIG. 1, contact
24C does not bridge terminal 24A to an internal terminal that is
connected internally of the combined devices to a terminal 26A of
motor 26. When coil 24S is energized, contact 24C connects the
positive battery bank terminals to motor terminal 26A so that
cranking current can operate motor 26, thereby cranking engine
14.
[0041] The truck electrical system comprises various load circuits,
designated generally by the reference 27 as Vehicle Electrical
Loads. A brief description of various loads is given here. A more
detailed description can be read in U.S. Pat. No. 6,836,094.
[0042] One or more fuse blocks are mounted at any suitable location
or locations on either the interior or exterior of the truck cab. A
fuse block contains multiple circuit protection devices, such as
fuses and/or circuit breakers, for distributing current to
individual circuits in the vehicle. The fuse blocks are battery-fed
through disconnect switch 12, and one battery-fed circuit allows
keyswitch 22 to operate motor 26 for cranking engine 14.
[0043] In addition to the group of circuits that are battery-fed, a
second group of circuits are accessory-fed, and a third group are
ignition-fed. In general, battery-fed circuits are those that are
appropriate for operation when keyswitch 22 is in OFF position,
although the switch is itself battery-fed. Accessory-fed circuits
are those for operating various accessory-type devices whose
operation, while not essential for engine starting and running, is
appropriate when the engine is not running, but nonetheless require
use of a key to operate switch 22 from OFF position. Any load that
the accessory circuits may be imposing on the batteries is removed
when the engine is being cranked. Ignition-fed circuits are those
for operating various devices whose operation is called for when
the engine is running or being started.
[0044] The placement of disconnect switch module 12 allows the
circuit between battery bank 16 and cranking motor terminal 24A to
be switch-free, providing important advantages that are described
in U.S. Pat. No. 6,836,094.
[0045] The embodiment of FIG. 2, which uses the same reference
numerals to designate the same elements as in FIG. 1, differs from
that of FIG. 1 only in that alternator terminal 20A is connected to
the battery side terminal 12A of switch module 12 instead of to the
load side terminal 12B.
[0046] FIG. 3 shows detail of the solid-state switch devices of
electronic disconnect switch module 12. This particular example
uses four solid-state devices 30A, 30B, 32A, and 32B. Each device
is a high-current, high-side switch, a specific example of which
was mentioned earlier. Devices 30A, 30B are arranged to form one
solid-state switch element, and devices 32A, 32B to form a second
solid-state switch element that is in parallel with the first. Each
switch element is connected between terminals 12A and 12B.
Additional pairs of switch devices, not specifically shown, may be
added to increased the current rating of the switch module.
[0047] The four devices 30A, 30B, 32A, and 32B are identical, and
detail of the internal construction of each is shown in FIG. 5,
using device 32A as the example. One of the internal elements is a
solid-state switch that comprises a source terminal 32AS, a drain
terminal 32AD, and a gate terminal 32AG. A junction forming a diode
32ADI is present between the source and drain terminals.
[0048] Two devices, such as 32A and 32B, form a switch element
(element 32) by connecting the drain terminals in common, as by a
connection 32C in FIG. 3. One source terminal, such as 32AS, is
connected to terminal 12A, and the other source terminal 32BS is
connected to terminal 12B. As many pairs of devices as are needed
to handle the load capacity of the electrical system are used in
any given disconnect switch, two pairs being the number in this
particular example. Devices 30A and 30B are connected in the same
way with a connection 30C connecting the drains in common.
[0049] A processor, such as microcontroller 34 in FIG. 3, is
associated with switch elements 30,32 in module 12 for both control
and information transmission purposes grouped for convenience into
the four feature groups referred to above: Vehicle Electrical
System Protection; Battery Charge Control; Battery Disconnect; and
Battery Monitoring. Microcontroller 34 communicates with various
vehicle electrical sub-systems, such as an electronic gauge cluster
(EGC) 35, a Vehicle Body Controller 36, and Aware.TM. Module 38, a
data link 40 as particularly shown in FIG. 4.
[0050] FIGS. 1, 2, and 4 show a reset switch 44 and an indicator 46
associated with disconnect switch module 12. Switch 44 is connected
to one of the inputs of module 12. Indicator 46 is connected to an
output of module 12 and can be, for example, an LED that is
integrated with switch 44. A manual disconnect switch 48 is
connected to the other input of module 12, enabling module 12 to
act as a Master Disconnect Switch specified by certain industry
standards. FIGS. 1, 2, 3, and 4 show the data link to be an SAE
J1939 data link. Additionally, FIG. 3 shows that the manual
disconnect input from switch 48 is conditioned by an analog signal
conditioning function 49 in module 12, that the reset switch input
is conditioned by an analog signal conditioning function 45, and
that it is via a high side output FET 47 that indicator 46 is
operated. Reset switch 44, when operated by the driver of the
vehicle after observing that indicator 46 is illuminated, can power
up the vehicle electrical system after module 12 has disconnected
the vehicle battery bank because a low battery charge condition has
been detected. It is assumed that the battery bank still can supply
enough electricity for resetting the disconnect switch module. FIG.
3 also shows that microcontroller 34 has communication with the
individual devices 30A, 30B, 32A, 32B via channels designated SI,
SO, SCLK, and CHIP SELECT. Interface to the microcontroller
utilizes the industry standard synchronous serial peripheral
interface (SPI) bus. This bus consists of four control lines from
the microcontroller to each high side switch:
[0051] The SI channel is used to transfer data from the master
(microcontroller) to the slave (switch). The SO channel is used to
transfer data from the slave to the master. The SCLK channel is
used as a common clock source between the two devices, generated by
the master. The control channels, SI, SO, and SCLK are common to
all high side switches.
[0052] The CHIP SELECT channel is used by the master to initiate
communications with a slave. Slaves will not communicate on the bus
unless their chip select line is in the proper state. The chip
select line is exclusive to each high side switch allowing the
microcontroller to communicate with each switch individually.
[0053] The SPI bus interface to the switch is used primarily for
control, configuration and diagnostics. Control of the switch is
mainly used to enable or disable the switch (on or off commands).
Configuration of the switch would include programming parameters
into the switch to enable current limit trip levels, slew rates and
others. Diagnostic information from the switch includes
overcurrent, open or shorted load, and others.
[0054] The Vehicle Electrical System Protection (VESP) feature
group serves to protect any electrical circuit or component that is
connected to the load side of module 12 from reverse battery
connection and certain jump-start conditions.
[0055] In a "reverse battery" condition, module 12 will disconnect
the vehicle battery bank from the vehicle electrical loads to
prevent battery voltage from being applied across electrical
components connected to load terminal 12B. The module contains
appropriate power supply circuitry so that it may remain powered
during a "reverse battery" condition in order to monitor the
continued presence of the "reverse battery" condition and to report
the duration of the condition, when a request is issued on data
link 40 to microcontroller 34. Once the reverse battery event has
been removed, the disconnect switch will connect the vehicle
battery bank back to the vehicle electrical loads.
[0056] Disconnect switch module 12 also protects any electrical
circuit or component connected to load terminal 12B during a
"double battery" jump-start condition. Such a condition is created
by connecting two nominal 12 VDC batteries in series to create a
nominal 24 VDC voltage source and then connecting the 24 VDC source
to between terminal 12A and ground. A "double-battery" jump-start
might be used in an attempt to start a vehicle with depleted
battery power.
[0057] Module 12 inherently provides protection against overvoltage
created by a "double battery" connection. Microcontroller 34 has
the ability to process data corresponding to the "double battery"
voltage being applied and to develop data for pulse width
modulation (PWM) of that voltage via the switching capabilities of
the high-current, high-side semiconductor switches forming switch
elements 30, 32. The processing and PWM capabilities of
microcontroller 34 are used to cause the switch elements 30, 32 to
pulse width modulate the "double battery" voltage so that the root
mean square (RMS) voltage at load terminal 12B corresponds to
nominal 14.2 VDC. Controlling the RMS voltage enables disconnect
switch module 12 to effectively regulate the DC voltage level
applied to electrical loads to a level that avoids undesired
overvoltage.
[0058] The Battery Charge Control feature group utilizes the
algorithm 50 shown in FIGS. 6A and 6B. The algorithm is programmed
in microcontroller 34 and iterates from time to time beginning at a
start point 52. A step 54 first determines the number of "Group 31"
batteries 18 in battery bank 16 and the total ampere-hour (AH)
capacity of the battery bank. The number of batteries in the bank
and the battery ampere-hour capacity are programmed parameters that
are programmed in the vehicle body controller 36, the programming
typically taking place on a production line where the vehicle is
being assembled. The vehicle body controller can then present the
programmed data to microcontroller 34 via the SAE J1939 data link
40.
[0059] A step 56 calculates a battery bank charge current (BBCC)
limit. For example, maximum ampere-hour charge current may be
limited to 20% of the total ampere-hour rating of the battery bank.
If the battery bank contained four "Group 31" batteries each rated
at 100 ampere-hours, the total ampere-hour rating of the bank would
be 400 ampere-hours. At a 20% limit, the maximum charge current
allowed to be delivered to the battery bank would be 80
amperes.
[0060] Once the maximum allowable BBCC has been determined, a step
58 measures the Closed System Charge Current (CSCC) and a step 60
measures the Open Circuit Voltage (OCV). The CSCC is the current
that in the closed system is produced by alternator 20, passes
through disconnect switch module 12, and enters battery bank 16 to
charge batteries 18. The OCV is the voltage measured by momentarily
operating disconnect switch module 12 to momentarily disconnect
battery bank 16 from the vehicle electrical system, and during
disconnection, measuring the no-load voltage of the battery bank.
Microcomputer 34 monitors the charge/discharge current level, OCV
level, and percentage to which the battery bank is considered fully
charged.
[0061] Using that data and the programmed data, microcomputer 34
performs calculations for determining which of three stages
describes the present condition of battery bank 16: Stage 1 (Bulk),
Stage 2 (Absorption), or Stage 3 (Maintenance/Float). The
determination uses what is essentially a decision tree, a brief
overview of which will be given before discussing details of the
algorithm of FIGS. 6A and 6B that implements the decision
process.
[0062] A first decision involves evaluating the battery bank
voltage relative to a threshold and the charge current relative to
a maximum limit. The results of those evaluations determine if the
battery bank condition is Stage 1 or alternatively another stage.
If they indicate the Stage 1 condition, a certain type of
regulation ensues.
[0063] If Stage 1 is not indicated, a second decision has to be
made, and it involves evaluating the battery bank charge current to
ascertain if it is within a 5%-20% range of the battery bank
ampere-hour rating calculated by step 54. If it is, then the Stage
2 condition is indicated, and another type of regulation ensues. If
it isn't. a Stage 3 condition is indicated by default.
Detailed Description of Stage 1
[0064] A step 62 determines if OCV is below a Stage 1 threshold
voltage (a voltage that is a programmable parameter for the
vehicle) or if BBCC is above 20% of the battery bank ampere-hour
rating. If OCV is below that threshold and BBCC is not above 20% of
the battery bank ampere-hour rating, a step 62 results in
microcomputer 34 operating switch 12 in a manner that regulates the
charge current from alternator 20 to battery bank 16 to ensure that
the BBCC maximum limit is not exceeded. In this stage, switch 12
does not regulate battery bank voltage, and so the battery bank
voltage will be approximately equal to the output voltage of
alternator 20. Periodically microcomputer 34 will check OCV (step
66). As long as OCV remains below the Stage 1 threshold, Stage 1
condition continues to be indicated and steps 64 and 66 repeatedly
iterate.
Detailed Description of Stage 2
[0065] However, when step 66 discloses that OCV is not below the
Stage 1 threshold voltage, a Stage 2 condition is indicated.
Microcomputer 34 will then begin to operate switch 12 to regulate
the battery bank voltage to the Stage 2 regulation level of 13.2V
(a voltage level that is also a programmable parameter for the
vehicle). Such operation is indicated by step 68 in FIG. 6B.
Depending on the alternator output voltage, the voltage supplied to
battery bank 16 could be lower than 13.2 VDC but will never be
greater than 13.2 VDC. In other words, disconnect switch 12 is not
to be operated to function as a boost regulator.
[0066] Had step 62 determined that OCV was not below the Stage 1
threshold voltage and that BBCC was not above 20% of the battery
bank ampere-hour rating, a step 70 would have determined if BBCC
was within the 5%-20% range of the battery bank ampere-hour rating
calculated by step 54, and if so the Stage 2 condition would have
been indicated, with step 68 being performed. (If not, the Stage 3
default state would be indicated--reference numeral 80).
[0067] Upon indication of the Stage 2 condition and ensuing
regulation of battery bank voltage to 13.2 VDC, a step 72
determines if BBCC is less than some percentage (10% in this
example) of the ampere-hour rating of the battery bank. If BBCC is
not less than that percentage, the algorithm executes step 66 which
then determines whether the battery bank is in Stage 1 or Stage 2
condition, with regulation continuing as previously described,
depending on whether the Stage 1 or the Stage 2 condition has been
indicated.
Detailed Description of Stage 3
[0068] If step 72 had determined that BBCC was below 5% of the
ampere-hour rating of the battery bank, Stage 3 would have been
indicated by default, and battery bank voltage would as a result
have been regulated to a further reduced voltage of 12.2 VDC (also
a programmable parameter) as indicated by a step 74. Once
regulation at the reduced level of 12.2 VDC has commenced, a step
76 determines if charge current has continued to remain below 5% of
the ampere-hour rating of the battery bank voltage. If so,
regulation at the 12.2 VDC level continues and step 76 is repeated.
The voltage supplied to the battery bank could be lower than 12.2
VDC but is not allowed to exceed 12.2 VDC. If BBCC rises to at
least the 5% level, then step 72 determines if the level has
returned to at least the 10% level. In this way, the Stage 3
condition continues to be indicated until the 10% level is again
reached after which step 66 occurs.
[0069] The Battery Disconnect feature group is used to disconnect
the vehicle battery bank from the vehicle electrical system. The
trigger mechanism for this feature is either automatic or manual.
In either case, disconnection is accomplished by turning off the
high-current, high-side semiconductor devices 30, 32 of disconnect
switch module 12 such that current is not allowed to flow from
battery terminal 12A to load terminal 12B.
[0070] Automatic disconnection is defined as disconnect switch
module 12 itself disconnecting the battery bank from the vehicle
electrical system. While engine 14 is off, i.e. not running,
disconnect switch module 12 monitors the battery voltage of battery
bank 16 through a software low pass filter. If the voltage
decreases below a programmable threshold level, disconnect switch
module 12 automatically disconnects battery bank 16 from the
vehicle electrical loads 27 to prevent further drain of the battery
bank. Once in this state, disconnect switch module 12 signals the
vehicle driver that battery bank 16 has been disconnected from the
vehicle electrical loads by periodically flashing indicator 46
inside reset switch 44. If reset switch 44 is pressed or closed by
the vehicle driver, disconnect switch module 12 re-connects battery
bank 16 to the vehicle electrical loads. Alternatively, module 12
re-connects the battery bank when engine is started and running.
Automatic disconnection can also be a result of a J1939 message
from another module such as the International Aware.TM. module.
This message could be used as a battery disconnect theft deterrent
feature. Manual disconnection is performed by operation of switch
48. At any time when engine 14 is off and not running, the driver
can manually disconnect the battery bank by pressing manual
disconnect switch 48. This feature is most useful for a service
technician who needs to remove battery power from the electrical
system for service purposes. This feature is useful in emergency
vehicles, for which applicable electrical system standards require
a battery disconnect switch that is operated by the vehicle
driver.
[0071] The Battery Monitoring features group uses the algorithm
method described in U.S. Pat. No. 6,417,668 to determine battery
bank condition.
[0072] The invention is believed to provide an improvement that
possesses attributes not heretofore contemplated for battery
disconnect switches in motor vehicles. While the invention provides
the basic function of avoiding unintended battery draining in a
motor vehicle when parked for an extended period of time, it
provides the added functions mentioned earlier in connection with
the four named feature groups.
[0073] While a presently preferred embodiment of the invention has
been illustrated and described, it should be appreciated that
principles of the invention are applicable to all embodiments that
fall within the scope of the following claims.
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